This invention is a continuous-flow extraction system and method for extracting oil from oil-bearing plant parts, or biomass, with liquid-phase hydrocarbon solvent, in a continuous process, with re-circulation and reuse of the solvent.
Presently, such extraction is performed on a batch basis, in part because there is a need to empty and clear the extractor vessel of spent and exhausted biomass, and to reload the vessel with fresh biomass. These processes in turn require a temporary shutdown of the extraction process. Additionally, present systems and methods do not provide for continuous regeneration of the used hydrocarbon solvent's properties, such that a smaller total amount of solvent can be used in an essentially closed, continuous loop.
Plant oils have been extracted from plant material for centuries. Many plant oils are extracted from seeds by squeezing or crushing the seeds to force out the oil therefrom. Mechanical oil extractors or expellers are extensively used for obtaining cold-pressed oils where the temperature of starting material does not exceed 120-degrees Fahrenheit. In order to increase the oil output, the oil extraction methods provide for the addition of heat and pressure.
In addition, plant oils can be extracted with the assistance of a chemical agent or solvent, such as hexane. Chemical extraction is cheaper and more efficient than mechanical extraction, at a large scale, leaving only 0.5-0.7% of the oil in plant solids, as compared to the 6-14% of mechanical extraction.
Plant seeds and pods are not the only plant components that contain oil. Fibrous plant matter, including leaves, flowers, and so forth, contain significant amounts of plant oil that can be extracted and used in cosmetics, healthcare industries, and the like. Many solutions have been developed to provide plant oil extraction.
For instance, U.S. Pat. No. 5,516,923 discloses a method of plant oil extraction, according to which grounded plant material is deposited into a reactor vessel, and vacuum is created in the reactor vessel. Liquid solvent is introduced into the reactor vessel and allowed to contact the plant material for a time sufficient to dissolve oil from the plant material, while the temperature in the reactor vessel is maintained at a level which prevents denaturing of constituent components of the plant oil and the plant material. Additional solvent vapors are introduced into the bottom of the reactor to cause mixing of the plant material and the solvent and separate fine particulate matter from heavier particles. Pressurized heated solvent vapors are introduced into the top of the reactor vessel while the liquid solvent and oil combination is being removed from the bottom of the reactor vessel through filters. To prevent clogging of filters in the bottom of the reactor vessel, pressurized solvent vapors are forced through the filters into the bottom of the reactor vessel. The solvent and oil combination is transferred into a separator vessel, wherein the solvent is vaporized and removed for recycling, while the oil is removed into a holding tank.
U.S. Pat. No. 7,002,029 discloses a process for solvent extraction of oils, in an extraction chamber. According to this method, solvent mist with significant adiabatic cooling is introduced into the extraction chamber, whereby a pressure difference between the solvent inlet and outlet of the extraction chamber drives the solvent mist through the raw oil material. The solvent is fed to the extraction chamber at pressures exceeding the atmospheric pressure, and the outlet of the extraction chamber is subject to a partial vacuum.
U.S. Application Publication No. 2003/0077367 discloses a process and system for extracting a solute from oil-bearing foodstuffs. This design uses a tubular membrane filter to separate a mass of the extracting medium and the foodstuffs into a miscella and foodstuffs of reduced oil content. In a batch or continuous process, after each extracting stage, the mass from the extraction vessel is conveyed to a membrane filter, which has pores along its cylindrical walls suitably sized to allow a miscella to pass as the permeate, while causing the foodstuffs of reduced oil content to be conveyed axially along the tubes and out of its ends as the retentate. This apparatus uses a heating jacket to provide heat by steam, either directly or indirectly. However, the heating jacket of this publication does not supply heat and cold to the interior of the separator vessel and the expansion filter and help evaporate and condense the solvent.
U.S. Application Publication No. 2009/0028971 discloses a method utilizing compressed hydrocarbons. Residues from the crop and fruit treatment, especially from the treatment of pips and berries, are used as starting materials. The method is carried out without organic solvents, while applying low pressures and reduced extraction agent throughputs. Preferred extraction agents are ethane, propane, butane, and the mixtures thereof, with the extraction itself being carried out in batches at pressures of less than 50 mPa and temperatures of approximately 70-degrees Celsius, with an extraction agent throughput of between 4 and 20 kg/kg of starting materials.
U.S. Application Publication No. 2011/0133120 teaches a method of plant oil extraction, which provides for a hermetically first tank coupled to a first valve, the first tank for storing a solvent comprising butane, an extraction zone comprising an extraction chamber coupled between the first valve and a second valve, the extraction chamber having a filter proximate to the second valve; the extraction chamber having a volume between one-fourth and one-sixth of the volume of the first tank. A filter separates flowing butane solvent and plant oil from organic plant material in the extraction chamber. A second tank has an exit valve for removing plant oil located on a bottom portion of the second tank, and an exit valve located near a top portion of the second tank. However, this design provides for the use of filter only at the bottom of the extraction zone.
U.S. Application Publication No. 2011/0100894 teaches a plant oil extraction device that has a main body member with a hollow interior that receives a plant. A filter member is removably mounted on the main body and has a groove therein that receives glass frit. Thus, when a solvent is placed in the hollow interior with the plant, the glass frit filters the plant particulate, allowing plant oil and solvent to flow into a receiving vessel. Once the oil is collected, the filter member may be removed from the main body such that the glass frit can be cleaned of all plant particulate and be reused.
A commercially available example of an extraction distillation unit is a Tamisium Extractor manufacture by TmiE of Cleburne, Tex. This extractor utilizes several different single solvents, and sometimes co-solvents, a primary solvent and a carrier solvent; in total three distinct types of extractions.
While the designs discussed above may work satisfactorily in different environments, there is a need for an easy-to-operate inexpensive apparatus for plant oil extraction that can be used in a non-industrial setting by a cosmetics laboratory, small shop, or consumer, without the need to mix solvents during an extraction process. During tests, it was also noted that the extraction process is made more efficient if the liquid material used to extract oil is maintained at a cooler temperature.